1. Field of the Invention
The present invention relates to a solid oxide fuel cell.
2. Description of Related Art
One of the conventional types of solid oxide fuel cells is a plate type. This type of solid oxide fuel cell has a laminate structure of cell units and interconnectors. Each cell unit comprises a solid electrolyte having a fuel electrode on one side and an air electrode on the other side, and conductive distributors which distribute a fuel gas (such as hydrogen) and air (or oxygen) entirely and evenly to the fuel electrode and the air electrode, respectively, and which also act as transmitters of electricity generated on the electrodes. The plate type solid oxide fuel cell has an advantage of having a large output per a unit volume. This is for the following reasons: By using thinner components, namely, thinner electrolytes and thinner interconnectors, a solid oxide fuel cell which contains more cell units keeping the same thickness can be obtained. Additionally, an electric current generated by the solid oxide fuel cell flows in the vertical direction, that is, in the thicknesswise direction, and the resistance is small. As a method of producing a thinner solid oxide fuel cell of this plate type, it has been suggested to sinter the components together after lamination of the components.
The electrodes are required to be excellently conductive and to be porous in such a degree as to allow gases to diffuse therein. Conventionally, a cerment of nickel and zirconium oxide has been used as the material of the fuel electrode. Generally, solid oxide fuel cells are operated at a temperature of about 1000.degree. C. for a long time, and during the operation, the cerment of nickel and zirconium oxide is being sintered to excess and losing its porosity. Moreover, if the above-mentioned producing method (sintering after lamination), in which the sintering temperature is over 1300.degree. C., is adopted, the porosity of the fuel electrode cannot be guaranteed.